White balance on skintones
It would be great to set the white balance not only to gray reference but also on a reference color, most importantly skin tones. This could be implemented by set references for skin colors or user definable values.
A lot of times one might not have a good reference within the picture when setting the balance manually. Also color shift is especially noticeable in skin tones and sometimes not too easy to correct, at least to me. Therefore I think this could save a lot of manual tweaking.
An implementation of this for ufraw can be found here: